Rotary impact tool



F. A. KAMAN 3,175,660

ROTARY IMPACT TOOL March 30, 1965 Filed Sept. 28, 1962 2 Sheets-Shea t 1 INVENTOR.

FRANK A. KAMAN March 30, 1965 ROTARY IMPACT TOOL 2 Sheets-$heet 2 43 52 6/ 44 55 I w. J24 .j

50 INVENTOR FRANK A. KAMAN BY mm, 117 a ATTYS.

United States Patent 3,175,660 ROTARY IIVIPACT TOOL Frank A. Kaman, Prospect Heights, 111., assignor to Skil Corporation, Chicago, 11]., a corporation of Delaware Filed Sept. 28, 1962, Ser. No. 227,006 Claims. (Cl. 192-30.5)

The present invention relates to rotary impact tools and more particularly to a new and improved rotary impact mechanism for such tools.

Rotary impact tools of the type to which the subject of this invention relates are preferably powered by hightorque, low inertia type air motors for providing high acceleration characteristics in rotatably driving the rotary impact mechanism. After each impact blow has been delivered by the rotary impact mechanism, the air motor powering such mechanism is temporarily stalled and must be allowed to rotate at least one revolution to allow it to accelerate to a suflicient angular velocity for delivering another full impact blow to the impact mechanism. Actually, after the delivery of each impact blow the rotary impact mechanism and motor rebound, i.e., rotate in a direction opposite to the direction of rotation when imparting impact blows, for approximately one-quarter to as much as one-half of a revolution. For purposes of acceleration of the air motor, this is a desirable feature in that the air motor accelerates as it rotates through the amount of rebound. It is desirable, however, to allow the air motor and rotary impact mechanism operably connected thereto to rotate a number of times between the delivery of impact blows in addition to the amount of rotation caused by rebound to permit suflicient acceleration of the rotary air motor.

Accordingly, it is a primary object of this invention to provide a new and improved portable rotary impact tool wherein a rotary mounted anvil having a tool engaging portion on the forward end thereof is provided with rotary impact blows by a rotatably driven hammer once during a predetermined number of revolutions of the hammer.

It is another important object of this invention to provide a new and improved portable rotary impact tool wherein the rotary hammer is driven by a rotary air motor and wherein the rotary hammer and air motor are adapted to rebound through a partial revolution after delivering each impact blow whereby the motor is allowed to accelerate through the amount of rebound plus a predetermined number of revolutions for increasing the impact force delivered to the rotatably mounted anvil.

It is a further object of the present invention to provide a new and improved rotary impact mechanism of the character described wherein the rotary hammer is provided with a pair of jaw members at its forward end which are projected forwardly once during a predetermined number of revolutions of the hammer whereby impact blows are delivered to the sides of radially extending impact receiving means formed on the anvil immediately forward of the front end of the hammer.

It is an even further object of the invention to provide a new and improved rotary impact mechanism wherein a plurality of novel rotary cam members are provided in the rotary hammer for projecting the jaw members forwardly once during a predetermined number of revolutions of the hammer member for delivering impact blows to radially extending impact receiving means formed on the anvil member immediately forward of the front end of the hammer.

It is a still further object of the invention to provide a new and improved rotary impact mechanism wherein a a minimum of moving parts thereby allowing a rotary impact of the kind described to be manufactured with ease and at a low cost.

3,175,660 Patented Mar. 30, 1965 It is a still further object of this invention to provide a new and improved rotary impact mechanism which is extremely rugged and durable in operation.

These and other objects and advantages of the invention will become apparent from the following specification wherein like numerals refer to similar par-ts throughout.

In the drawings:

FIG. 1 is a vertical central section taken through a portable rotary impact tool embodying the invention and showing the jaw members of the hammer in their forwardly projected position for delivering impact blows to the side edges of radially extending arms on the anvil member;

FIG. 2 is a section taken on the line 22 of FIG. 1;

FIG. 3 is a section similar to FIG. 2 but showing the jaw members delivering impact blows to the side edges of the radial arms on the anvil member;

FIG. 4 is a section taken along line 4-4 of FIG. 1 showing the rotary cam members in plan view;

FIG. 5 is a longitudinal section taken through the center of one of the rotary cam members of the impact mechanism of this invention;

FIG. 6 is a view taken along the line 66 of FIG. 5; and

FIG. 7 is a vertical central section of the forward portion of a rotary impact tool showing the jaw members of the hammer in their rearward or retracted position.

As illustrated in FIG. 1, a portable rotary impact tool, generally designated 10, embodying the rotary impact mechanism of this invention includes a housing structure 11 characterized by a forwardly projecting barrel portion 12 bolted thereto and by a depending hand grip 13. A rotary accelerating device, such as an air motor 14 of known type, is provided in the rear end of the housing port-ion 11. The air motor 14 includes a fixedly mounted stator structure 15 having a rotor element 16 which extends therethrough, which rotor has a series of vanes 17 associated therewith. The rotor element 16 is rotatably supported in the stator structure 15 in ball bearings 18 and 19. The forward end of the rotor element 16 is provided with a spline formation 20 for driving engagement with the rotary impact mechanism as will be referred to hereinafter. Whatever known type of rotary accelerating device is utilized in the rotary impact tool 10, it should preferably be a high-torque, low inertia device for providing high acceleration characteristics to rotatably drive the impact mechanism to be described.

When air under pressure is directed to the air motor 14, the rotary element 16 thereof will be rotatably driven in a manner well known in the art. A reversing valve member 22, which is manually shiftable transversely of the rotary impact tool between two operable positions, is adapted in one position to direct air under pressure to the air motor 14 in a manner whereby the rotor element 16 will be rotated in 'a clock-Wise direction, as viewed from the rear end of the tool, and in its other position to direct air under pressure to the air motor in a manner whereby the rotor element will be rotated in a counterclockwise direction, as viewed from the rear end of the tool.

Air under pressure is directed to the reversing valve 22 through a series of passages, chambers and valves provided in the hand grip portion 13 of the housing structure 11. In the rotary impact tool illustrated in FIG. 1, an air pressure line or conduit is adapted to be connected to an air inlet connector 24 having an air filter element 25 associated therewith. After passing through the air filter element, the air under pressure is directed through a passage 26 to an aperture 27 in communication with a chamber 28. A passage 29 leads from the chamber 28 into a chamber 30. The entrance end of the chamber 28 is controlled by a valve member 31, which valve member is opened by the operator of the tool prior to the commencing of an operation with the tool for permitting air under pressure to be directed into the chamber 30 which is normally closed by a plunger-type valve 32 of known type. The valve 32, which is normally retained in its closed position by a spring member 33, may be readily opened by pressing inwardly on a depressible plunger head 34 which is disposed forwardly from the front surface of the hand grip 13. Pressing of the plunger head 34 permits air under pressure to pass from the chamber 30 into a passage 35 and then into a chamber 36 which is in communication with the reversing valve 22. The plunger head 34 of the valve 32 is positioned for convenient operation by a persons index or trigger finger.

The invention is primarily directed to a novel rotary impact mechanism for the rotary impact tool 10. Briefly and by way of introduction, the rotary impact mechanism includes a generally cylindrical hammer member 40 which is adapted to be rotatably driven by the rotary accelerating device 14, a pair of jaw members 41 adapted to be projected forwardly once during a predetermined number of revolutions of the hammer member, a tool supporting anvil 42 having impact receiving means formed thereon adapted to receive impact blows from the jaw members, and a pair of rotary cam members for actuation of the jaws.

The hammer member 40, which is rotatably mounted in the forwardly projecting barrel portion 12 of the housing structure, is generally cylindrical having a flat face 43 closing the rear end thereof, which face has an integral rearwardly extending neck portion 44 with an inner spline formation 45 adapted for driving engagement with the spline formation 20 provided on the forward end of the rotary element 16 of the air motor 14. The neck portion 44 of the hammer member is rotatably supported in a plurality of ball bearings 46.

The jaw members 41, which are preferably pins formed of hardened steel, are mounted in the forward portion of the hammer member 40 in diametrically oppositely disposed apertures 47 formed in the front surface of the hammer member. Each aperture 47 is coaxial with a bore 48 formed in the hammer member, which bore is adapted to slidably receive an annular shoulder 49 provided at the rear end of each of the jaws 41. Each jaw 41 is encircled by a coil spring 50 adapted to be received in the annular space defined by the inside of the bore 48 and the outside of the jaw 41, which spring constantly urges the jaw to its rearwardmost position in the hammer member. The rear end of each of the jaws 41 is provided with an axially extending rounded tip 51 adapted to be engaged by a rotary cam member which will be referred to in greater detail hereinafter.

The anvil member 42 is rotatably mounted by a plurality of roller bearings 52 in a sleeve 53, which sleeve is secured in the nose of the barrel portion 12 extending from the housing 11. The anvil 42 has a rearwardly disposed shank portion 54 extending coaxially through a central bore 55 in the cylindrical hammer member 40, and it is rotatably supported therein by a plurality of roller bearings 56. It will be realized that the anvil is adapted to rotate with and relative to the hammer member. A plurality of axially extending teeth 57 are provided on the exterior of the shank portion 54 at the rear end thereof. Extending forwardly on the anvil member 42 is a tool engaging portion 58, which tool engaging portion is adapted to be non-rotatably and detacha-bly received in a socket of an appropriate working tool member. Radially extending impact receiving means or arms 59, as best seen in FIGS. 2 and 3, are provided on the anvil member 42 just forward of the front surface of the hammer member 40. As will be referred to in greater detail below, the impact receiving arms 59 are adapted to receive impact blows from the jaws 41, which jaws are projected forwardly into a position for striking the arms once during a predetermined number of revolutions of the hammer member. Oppositely disposed arcuate depressions 59a are provided at the side edges of each of the arms 59 for accommodating the circular in crosssection jaws 41. The impact blow delivered to the anvil 42 through the radially extending arms 59 is a balanced one since the jaws 41 simultaneously contact, respectively, the radially extending arms. The provision of a balanced impact blow permits the impact tool to be operated with ease and with comfort to the operator and substantially reduces the stresses and strains on the various parts of the impact tool.

The portion of the rotary impact mechanism for projecting the jaws 41 forwardly into their impact delivering position and for permitting them to retract to clear the impact receiving means of the anvil member during acceleration of the rotary air motor will now be described. A pair of diammetrically oppositely disposed rotary cam members 60 are rotatably mounted against the inside of the face 43 of the rotary hammer member. The rotary cams are mounted on pins 61, which pins are adapted to be threaded in interiorly threaded apertures provided in the face plate 43. As best seen in FIGURES 5 and 6, each member 60 has a plurality of teeth 62 extending around the periphery thereof and a central axially extending bore 63 adapted to rotatably receive the pin 61. An annular cam surface 64 is concentrically disposed on the forward face of each rotary cam member, which cam surface is flat over its major portion and has a single cam lobe 65 projecting outwardly from a sector shaped segment thereof. As will be noted by reference to FIGURE 4, the sector defined by the cam lobe is approximately 60 degrees. Preferably, this sector on the annular cam surface is always less than degrees.

By referring to FIGURE 1 it will be observed that the cam members 60 are rotatably mounted in the rotary hammer member in a plane which is 90 degrees to the central axis of rotation of the hammer member. The central axis of each of the rotary cams is inwardly offset from the central axis of is respective jaw 41 for a distance which is equal to the radius of the annular cam surface 64, i.e., the radius to the center line of the cam surface. The mounting of the rotary cams 60 in this fashion will place a point on each center line of the cam surfaces thereon in alignment with respective central axes of the jaws 41, whereby the rearwardly extending rounded tips 51 provided on the jaws 41 will always be in alignment with points on the annular cam surfaces. It will be apparent that rotation of the members 60 with respect to the hammer member 40, i.e., rotation of the cams about their respective central axes, will bring the forwardly projecting lobes 65 thereon into contact with corresponding tips 50 on the jaws 41 for imparting forward sliding movement to the jaws in the hammer member. The jaws are shown in their forwardmost or impact delivering position in FIGURE 1, and in their rearwardmost or retracted position in FIGURE 7. It will also be observed by reference to FIGURES 1 and 7, that the teeth 62 provided at the peripheries of the rotary cams 60 are adapted to mate with the teeth 57 provided on the rear end of the shank 54. Rotary interengagement of these teeth results in the imparting of relative rotary movement between the rotary earns 60 and the rotary hammer member 40. It will be observed that there is no direct contact between the shank 54 of the anvil member and the face 43 of the hammer member. Although the rotary cam members in the embodiment shown comprise rotary gear members, it will be realized that other means for imparting rotation to these members, such as a chain or friction drive, could be used.

The operation of the rotary impact mechanism of this invention is as follows:

When the rotary impact tool is at rest, the jaws 41 will be in their rearwardmost position with the rounded tips thereof in contact with the fiat portion of the annular cam surfaces 64 on the rotary cam members 60. With the jaws 41 in this position the front ends thereof will be disposed rearwardly of the front surface of the rotary hammer member. Manifestly, it is necessary that the jaws 41 operate simultaneously in imparting an impact blow to the anvil member. Accordingly, each of the rotary cams 60 must be mounted in timed relation with respect to the shank 54. During assembly of the rotary impact mechanism, the teeth of the rotary cams are mated with the teeth on the shank portion to allow both cam lobes 65 to engage simultaneously the corresponding tips of the jaws 41.

An appropriate working tool is attached to the tool engaging portion 58 of the anvil member, and air under pressure is admitted to the rotary air motor 16 by means of the valves 31 and 32, the latter of which is actuated by depressing the finger plunger head 34. This will result in rotation, say in a clockwise direction depending on the position of the slide valve 22, of the air motor and the rotary hammer member 40 which is operably secured thereto. If the working tool attached to the anvil is not contacting a workpiece, i.e., if no force is applied to restrain rotary movement of the anvil, the entire anvil will rotate about the central axis thereof along with the rotary hammer member. This is because of the engagement between the teeth of cam-s 6t) and spline formation 57 of the anvil. When rotation of the anvil is not being resisted, cams 60 do not rotate relative to the hammer either by reason of frictional engagement with pins 61 and the front face of plate 43 or by reason of engagement of the cam lobes with the rounded tips of the jaws, this engagement not being sufiicient in magnitude to overcome the force of the jaw springs. It will be apparent that as the hammer rotates, the rotary cams and the jaws which are mounted therein wiil rotate about the central axis of the hammer member in planes perpendicular to this central axis. Since the anvil 42 is rotating with the hammer member there will be no relative movement between the rotary cams and the hammer, and consequently forward movement will not be imparted to the jaw members and impact blows will not be imparted to the anvil member. The various parts remain in their above described relationship during run-up of a nut being rotated. When rotary movement of the anvil is restrained, as for example when a nut being run begins to seat or otherwise resist rotation, relative rotary movement will result between the anvil member and the hammer member. Because of the interengagement of the teeth 62 on the rotary cam members with the teeth 57 on the shank portion on the anvil, this relative movement between the anvil and hammer will produce rotary movement of the cams 60 about the respective central axes thereof. As the rotary cams 60 rotate in the same direction about their own central axes, the forwardly projecting cam lobes 65 thereon will be brought into contact with the rounded tips 51 at the rear end of the jaw members. As the tips ride up on the cam lobes, the jaws will be simultaneously projected forwardly in the hammer member for delivering an impact blow to the radially extending arms 59 on the anvil member.

By reference to FIGURE 2, which shows the relationship of the jaws and the radially extending arms on the anvil member when the jaws have just reached their forwardmost position, it will be noted that the jaws must travel through approximately 60 of rotation before they will contact the side edges of the radially extending arms for delivering impact blows thereto. During this continued rotation of the hammer member from the point where the jaws have reached their forwardmost position, the rotary cams 60 will continue to rotate relative to the hammer thereby moving the cam lobes out of contact with the tips on the rear ends of the jaws. However, be cause of the angular velocity of the rotary hammer member and because of the inertia of the jaws caused by the rapid forward movement imparted thereto, the front ends thereof will be extended forwardly of the front surface of the rotary hammer member when the jaws are in the location shown in FIGURE 3 for delivering impact blows to the radially extending arms, notwithstanding the fact that the jaw tips 51 are no longer in contact with the cam lobes. In other words, at the exact instant of impact the tips of the jaws are disengaged from the cam lobes and are spaced apart from the flat portions of the annular cam surfaces. Shortly after impact the springs 50 will return the jaws to their fully retracted position. After an impact blow has been delivered by the rotary hammer, the hammer and air motor operably connected thereto tend to rebound, i.e. rotate in a direction opposite to the direction of rotation when delivering impact blows. During rebound relative movement results between the anvil member and the hammer member, but this relative movement is, of course, opposite to the relative movement that resulted when the jaw members were being projected forwardly. During this rebound, which may be one quarter or even one half of a revolution, the rounded tips on the jaws may tend to be engaged again by the cam lobes which would project the jaws forwardly during this period of rebound. However, after the rotary hammer fully rebounds and its direction of rotation is reversed by the rotary air motor, relative movement between the anvil and rotary hammer will again be reversed which will result in reversing the direction of the rotary movement of the rotary cams thereby permitting the jaws 41 to retract by means of the springs to a position wherein the front ends thereof are disposed rearwardly of the front surface of the hammer member. When the hammer begins its acceleration, i.e. just after it has fully rebounded, its velocity is much less than its velocity at impact; this provides more time for the jaw springs to retract the jaws before they pass the anvil arms upon acceleration of the hammer. The jaws are allowed to be moved rearwardly by the springs since the rounded tips of the jaws are disengaged from the cam lobes before the jaws pass the anvil arms during initial acceleration of the hammer. In this way the forward ends of the jaws will not contact the radially extending arms on the anvil as the air motor begins to accelerate through a predetermined number of revolutions for delivering another impact blow to the anvil member.

It will be apparent that the rotary motor must rotate the hammer through a number of revolutions sufiicient to impart one revolution to the rotary cams about the respective axes thereof before another impact blow will be delivered to the anvil member. Manifestly, the number of revolutions of the .hammer member per one revolution of each of the rotary gears relative thereto will depend on the ratio of the number of teeth of the anvil shank with the number of teeth on each of the rotary cams. For example, the provision of twice the number of teeth on each of the rotary cams as the number of teeth on the anvil shank will result in one revolution of each of the rotary cams relative to the hammer for every two revolutions of the rotary hammer member. Of course, this ratio of the number of teeth on each of the rotary cams to the number of teeth on the anvil shank can be varied as desired. It has been found that a tool having a rotary impact mechanism with teeth at a two to one ratio, i.e. two revolutions of the hammer member for a single revolution of each rotary cam relative to the hammer member, has resulted in a tool of markedly increased efficiency in the delivering of impact blows. Because the rotary hammer and air motor connected thereto are allowed to rotate through two complete revolutions plus the amount of rebound, the rotary air motor is given an opportunity to accelerate to a velocity where it will be able to rotate the hammer member to deliver effectively impact blows. This important feature provides a rotary impact tool of greatly increased operating characteristics. As stated above, this ratio of the number of revolutions of the hammer member per revolution of the rotary cams s,175,eeo

7 relative thereto can be varied as required, but in no case would more than a four to one ratio be necessary as a conventional rotary air motor will fully accelerate within four revolutions.

It will be apparent that the rotary impact mechanism of this invention is adapted to deliver impact blows while rotating in either a clockwise or counterclockwise direction. It will be recalled that the direction of rotation of the rotary air motor 16 may be changed by actuating the reversing valve 22. It will be noted that clockwise as well as counterclockwise operation of the rotary impact mechanism is permitted by making the jaw tips symmetrical and by making the cam lobes 65 symmetrical with respect to a longitudinal plane taken through the center of the rotary cams at the tips of the lobes. Also, functioning of the impact mechanism in both directions is made possible by providing recesses 59a on opposite edges of each of the radially extending impact receiving arms 59.

Thus it will be seen that by this invention a new and improved rotary impact mechanism has been provided for a rotary impact tool, which impact mechanism is adapted to deliver impact blows once during a predetermined number of revolutions of the air motor powering the tool. By this invention after each impact blow is delivered, the rotary air motor is allowed to accelerate through the predetermined number of revolutions plus the amount of rebound, thereby allowing the motor to deliver successive powerful impact blows during operation of the tool. It will also be realized that the rotary impact mechanism of this invention contains but few moving parts which allows the tool to be manufactured with ease and at a low cost. Further, because few parts are used the likelihood of breakdowns of the tool is remote. The construction of the rotary impact mechanism of this invention readily lends itself to varying the ratio of revolutions of the hammer between impact blows. This is accomplised by merely changing the ratio of the number of teeth on the individual rotary cam members to the number of teeth on the shank portion of the anvil member.

While the invention has been shown in but one form it will be obvious to those skilled in the art that it is not to be so limited, but rather it is susceptible to various changes and modifications without departing from the spirit and scope of the appended claims.

I claim:

1. In a rotary impact tool having rotary motor means, a rotary impact mechanism comprising, a hammer member operably connected to said rotary motor means for rotation therewith, a generally cylindrical anvil member having a shank portion extending co-axially into said I surface thereof, a plurality of equally spaced jaw members mounted in said hammer member for rotation therewith around the central axis of said hammer member and for reciprocating movement parallel to said axis, means resiliently urging each of said jaw members into a rearward position wherein the front ends thereof are disposed rearwardly of said impact receiving means, a plurality of rotary cam members mounted in the rear end of said hammer member for actuation, respectively, of said jaw members, said rotary cam members being mounted to rotate with said hammer member around the central axis thereof in a plane perpendicular to said axis, each of said rotary cam members also being mounted to rotate about its own central axis and having a cam surface thereon adapted for engagement with the rear end of the associated jaw member for camming the latter forwardly, whereby forward sliding movement is imparted to said jaw members during rotation of said rotary cam members about the respective central axes thereof, means for rotating said rotary cam members one revolution about the respective central axes thereof during a predetermined number of revolutions of said hammer member relative to the anvil, whereby said jaw members are projected forwardly into position for delivering impact blows to said impact receiving means once during said predetermined number of revolutions of said hammer member, each of said jaw members being fully cammed forwardly in advance of striking the impact receiving means so that each of said cam surfaces is disengaged from the rear end of the associated jaw member at the time of impact thereby to permit said resilient means to return each jaw member to its rearward position.

2. In a rotary impact tool having rotary motor means, a rotary impact mechanism comprising, a hammer member operably connected to said rotary motor means for rotation therewith, a generally cylindrical anvil member having a shank portion extending co-axially into said hammer member, said anvil member being rotatable with and relative to said hammer member, radially extending impact receiving means formed on said anvil member forward of said hammer member and adjacent the front surface thereof, a plurality of equally spaced jaw members mounted in said hammer member for rotation therewith around the central axis of said hammer member and for reciprocating sliding movement parallel to said axis, means resiliently urging each of said jaw members into a rearward position wherein the front ends thereof are disposed rearwardly of said impact receiving means, a plurality of rotary cam members mounted in the rear end of said hammer member for actuation, respectively, of said jaw members, said rotary cam members being mounted to rotate with said hammer member around the central axis thereof in a plane perpendicular to said axis, each of said rotary cam members also being mounted to rotate about its own central axis in said plane and having a cam surface projecting from the forward face thereof for engagement with the rear end of the associated jaw member for camming the latter forwardly, whereby forward sliding movement is imparted to said jaw members during rotation of said rotary cam members about the respective central axes thereof, means operable by relative rotation between the hammer and the anvil for rotating said rotary cam members one revolution relative to said hammer member during a predetermined number of revolutions of said hammer member relative to said anvil, whereby said jaw members are projected forwardly into position for delivering impact blows to said impact receiving means once during said predetermined number of revolutions of said hammer member, each of said jaw members being fully cammed forwardly in advance of striking the impact receiving means so that each of said cam surfaces is disengaged from the rear end of the associated jaw member at the time of impact thereby to permit'said resilient means to return each jaw member to its rearward position.

3. In a rotary impact tool having rotary motor means, a rotary impact mechanism comprising, a hammer member operably connected to said rotary motor means for rotation therewith, a generally cylindrical anvil member having a rearwardly disposed shank portion extending' co-axially into said hammer member, said anvil member being rotatable with and relative to said hammer member, radially extending impact receiving means formed on said anvil member forward of said hammer member and adjacent the front surface thereof, a plurality of equally spaced jaw members mounted in said hammer member for rotation therewith around the central axis of said hammer member and for reciprocating sliding movement parallel to said axis, means resiliently urging each of said jaw members into a rearward position wherein the front ends thereof are disposed rearwardly of said impact receiving means, a plurality of rotary cam members mounted in rear end of said hammer member for actuation, respectively, of said jaw members, said rotary cam members being mounted to rotate with said hammer member around the central axis thereof in a plane perpendicular to said axis, each of said rotary cam members also being mounted to rotate about its own central axis in said plane and having a cam surface projecting from the forward face thereof for engagement with the rear end of the associated jaw member for camming the latter forwardly, whereby forward sliding movement is imparted to said jaw members during rotation of said rotary cam members about the respective central axes thereof, said rotary cam members having the respective peripheries thereof engageable with the periphery of the shank portion of said anvil member for rotating each of said rotary cam members one revolution relative to said hammer member during a predetermined number of revolutions of said hammer member relative to the anvil, whereby when rotary movement of said anvil is restrained said hammer member is rotated relative to said anvil member thereby projecting said jaw members forwardly into position for delivering impact blows to said impact receiving means once during said predetermined number of revolutions of said hammer member, each of said jaw members being fully cammed forwardly in advance of striking the impact receiving meansso that each of said cam surfaces is disengaged from the rear end of the associated jaw member at the time of impact thereby to permit said resilient means to return each jaw member to its rearward position.

4. In a rotary impact tool having rotary motor means, a rotary impact mechanism comprising, a hammer member connected to said rotary motor means for rotation therewith, a generally cylindrical anvil member having a rearwardly disposed shank portion extending co-axially into said hammer member, which shank portion has a plurality of teeth formed exteriorly on the rear end thereof, said anvil member being rotatable with and relative to said hammer member, radially extending impact receiving means formed on said anvil member forward of said hammer member and adjacent the front surface thereof, a plurality of equally spaced jaw members mounted in the front end of said hammer member for rotation therewith around the central axis of said hammer member and for reciprocating sliding movement parallel to said axis, means resiliently urging each of said jaw members into a rearward position wherein the front ends thereof are disposed rearwardly of said impact receiving means, a plurality of rotary gears mounted in the rear end of said hammer member for actuation, respectively, of said jaw members, said rotary gears being mounted to rotate with said hammer member around the central axis thereof in a plane perpendicular to said axis, each of said rotary gears also being mounted to rotate about its own central axis in said plane and having a cam surface projecting from the forward face thereof for engagement with the rear end of the associated jaw member for camming the latter forwardly, whereby forward sliding movement is imparted to said .jaw members during rotation of said rotary gears about the respective central axes thereof, each of said' rotary gears having teeth at the periphery thereof engageable with the teeth on said shank portion of said anvil for rotating each of said rotary gears one revolution relative to said hammer member during a predetermined number of revolutions of said hammer member relative to the anvil, whereby when rotary movement of said anvil member is restrained said hammer member is rotated relative to said anvil member thereby projecting said jaw members forwardly into position for delivering impact blows to said impact receiving means once during said predetermined number of revolutions of said hammer member, each of said jaw members being fully cammed forwardly in advance of striking the irnpact receiving means so that each of said cam surfaces is disengaged from the rear end of the associated jaw member at the time of impact thereby to permit said resilient means to return each jaw member to its rearward position.

5. The rotary impact mechanism according to claim 4 wherein the number of teeth on each of said rotary gears is at least twice the number of teeth of said shank portion.

6. In a rotary impact tool having rotary motor means, a rotary impact mechanism comprising, a generally cylindrical hammer member operably connected to said rotary motor means for rotation therewith, a generally cylindrical anvil member having a rearwardly disposed shank portion extending co-axially into said hammer member, which shank portion has a plurality of teeth formed exteriorly on the rear end thereof, said anvil member being rotatable with and relative to said hammer member, a pair of equally spaced radially extending arms formed on said anvil member forward of said hammer member and adjacent the front surface thereof, a pair of diametrically oppositely disposed jaw members mounted in the front end of said hammer member for rotation therewith around the central axis of said hammer member and for reciprocating sliding movement parallel to said axis, means resiliently urging each of said jaw members into a rearward position wherein the front ends thereof are disposed rearwardly of said arms, a pair of diametrically oppositely disposed rotary gears mounted in the rear end of said hammer for actuation, respectively, of said jaw members, said rotary gears being mounted to rotate with said hammer member around the central axis thereof in a plane perpendicular to said axis, each of said rotary gears also being mounted to rotate about its own central axis in said plane and having a single lobe .cam surface projecting from the forward face thereof for engagement with the rear end of the associated jaw member for camming the latter forwardly, whereby forward sliding movement is imparted to said jaw members once during a single revolution of said rotary gears about the respective central axis thereof, each of said rotary gears having teeth at the periphery thereof engageable with the teeth of said shank portion of said anvil for rotating each of said rotary gears one revolution relative to said hammer member during a predetermined number of revolutions of said hammer member relative to the anvil, whereby said jaw members are projected forwardly into position for delivering impact blows to said impact receiving means once during said predetermined number of revolutions of said hammer members, each of said jaw members being fully cammed forwardly in advance of striking the arms so that each of said cam lobes is disengaged from the rear end of the associated jaw member at the time of impact thereby to permit said resilient means to return each jaw member to its rearward position.

7. In a rotary impact tool having rotary motor means, a rotary impact mechanism comprising, a generally cylindrical hammer member operably connected to said rotary motor means for rotation therewith, a generally cylindrical anvil member having a rearwardly disposed shank portion extending co-axially into said hammer member, which shank portion has a plurality of teeth formed exteriorly on the rear end thereof, said anvil member being rotatable with and relative to said hammer member, radially extending impact receiving means formed on said anvil member forward of said hammer member and adjacent the front surface thereof, a pair of diametrically oppositely disposed generally cylindrical jaw members mounted in the front end of said hammer member for rotation therewith around the central axis of said hammer member and for reciprocating axial movement parallel to said axis, means resiliently urging each of said jaw members into a rearward position wherein the front ends thereof are disposed rearwardly of said impact receiving means, a pair of diametrically oppositely disposed rotary gears mounted in the rear end of said hammer member for actuation, respectively, of said jaw members, said rotary gears being mounted to rotate with said hammer member around the central axis thereof in a plane perpendicular to said axis, each of said rotary gears also being mounted to rotate about its own central axis in said plane and having an annular cam surface concentrically disposed on the forward face thereof, each of said rotary gears having the central axis thereof laterally offset from the central axis of said respective jaw member for a distance equal to the radius of said annular cam surface, a single cam lobe projecting forwardly from each of said cam surfaces for engagement with the rear end of the associated jaw member for camming the latter forwardly, whereby forward sliding movement its imparted to said jaw members once during a single revolution of said rotary gears about the respective central axes thereof, each of said rotary gears having teeth at the periphery thereof engageable with the teeth of said shank portion of said anvil for rotating each of said rotary gears one revolution relative to said hammer member during a predetermined number of revolutions of said hammer member relative to the anvil, whereby when rotary movement of said anvil is restrained, said hammer member is rotated relative to said anvil member thereby projecting said jaw members forwardly into position for delivering impact blows to said impact receiving means once during said predetermined number of revolutions of said hammer member, each of said jaw members being fully cammed forwardly in advance of striking the impact receiving means so that each of said cam lobes is disengaged from the rear end of the associated jaw member at the time of impact thereby to permit said resilient means to return each jaw member to its rearward position.

8. In a rotary impact tool having rotary motor means, a rotary impact mechanism comprising, a generally cylindrical hammer member having a flat face at the rear end thereof, which hammer member is operably connected to said rotary motor means for rotation therewith, a generally cylindrical anvil member having a rearwardly disposed shank portion extending coaxially into said hammer member, which shank portion has a plurality of teeth formed exteriorly on the rear end thereof, said anvil member being rotatable with and relative to said hammer member, radially extending impact receiving means formed on said anvil member forward of said hammer member and adjacent the front surface thereof, a pair of diametrically oppositely disposed generally cylindrical jaw members mounted in the front end of said hammer member for rotation therewith around the centralaxis of said hammer member and for reciprocating axial movement parallel to said axis, means resiliently urging each of said' jaw members into a rearward position wherein the front ends thereof are disposed rearwardly of said impact receiving means, a pair of diametrically oppositely disposed rotary gears rotatably mounted against the inside of said flat face for actuation, respectively, of said jaw member and thereby being supported to rotate with said' hammer member around the central axis thereof in a plane perpendicular to said axis, each of said rotary gears also being mounted to rotate about its own central axis in said plane and having an annular cam surface concentrically disposed on the forward face thereof, each of said rotary gears having the central axis thereof laterally offset inwardly from the central axis of said respective jaw member for a distance equal to the radius of said annular cam surface, a single cam lobe projecting forwardly from each of said cam surfaces for engagement with the rear end of the associated jaw member for camming the latter forwardly, whereby forward sliding movement is imparted to said jaw members once during a single revolution of said rotary gears about the respective central axes thereof, each of said rotary gears having teeth at the periphery thereof engageable with the teeth of said shank portion'of said anvil for rotating each of said rotary gears one revolution relative to said hammer member during a predetermined number of revolutions of said hammer member relative to the anvil, whereby when rotary movement of said anvil is restrained said hammer member is rotated relative to said anvil member thereby project ing said jaw members forwardly into position for delivering impact blows to said impact receiving means once during said predetermined number of revolutions of said hammer member, each of said jaw members being fully cammed forwardly in advance of striking the impact receiving means so that each of said cam lobes is disengaged from the rear end of the associated jaw member at the time of impact thereby to permit said resilient means to return each jaw member to its'rearward position.

9. In a rotary impact tool having rotary motor means, a rotary impact mechanism comprising, a generally cylindrical hammer member having a flat face at the rear end thereof, which hammer member is operably connected to said rotary means for rotation therewith, a generally cylindrical anvil member having a rearwardly disposed shank portion extending co-axially into said hammer member, which shank portion has a plurality of teeth formed exteriorly on the rear end thereof, said anvil member being rotatable with and relative to said hammer member, radially extending impact receiving means formed on said anvil member forward of said hammer member and adjacent the front surface thereof, a pair of diametrically oppositely disposed jaw pins mounted in the front end of said hammer member for rotation therewith around the central axis of said hammer member and for reciprocating axial movement parallel to said axis, means resiliently urging each of said jaw pins into a rearward position wherein the front ends thereof are disposed rearwardly of said impact receiving means, each of said jaw pins having an axially extending rounded tip at the rear end thereof, a pair of diametrically oppositely disposed rotary gears mounted against the inside of said flat face for actuation, respectively, of said jaw members and thereby being supported to rotate with said hammer member around the central axis thereof in a plane perpendicular to said axis, each of said rotary gears also being mounted to rotate about its own central axis in said plane and having an annular cam surface concentrically disposed on the forward face thereof, each. of said rotary gears having the central axis thereof laterally offset inwardly from the central axis of said respective jaw'pin for a distance equal to the radius of said annular cam surface, a single cam lobe projecting forwardly from each of said cam surfaces for engagement with the tip of the associated jaw member for camming the latter forwardly, each of said. lobes being symmetrical with respect to a plane passing through the high point of the lobe and containing the central axis of the associated rotary gear, whereby forward sliding movement is imparted to said jaw pins once during a s'ngle revolution of said rotary gears about the respective central axes thereof, each of said rotary gears having teeth at the periphery thereof engageable with the teeth of said shank portion on said anvil for rotating each of said rotary gears one revolution relative to said hammer member during a predetermined number of revolutions of said hammer member relative to the anvil, whereby when rotary movement of said anvil is restrained, said hammer member is rotated relative to said anvil member thereby projecting said jaw pins forwardly into posi tion for delivering impact blows to said impact receiving means once during said predetermined number of revolutions of said hammer member, each of said jaw members being fully cam-med forwardly in advance of striking the impact receiving means so that each of said cam lobes is disengaged from the rear end of the associated jaw member at the time of impact thereby to permit said resilient means to return each jaw member to its rearward position.

10. In a rotary impact to-ol having rotary motor means, a rotary impact mechanism comprising, a generally cylindrical h ammer mernber having a flat face at the rear end thereof, which hammer member is opera y connected to said rotary means for rotation therewith, a generally cylindrical anvil member having a rearw'ardly disposed shank portion extending co-axially into said hammer member, which shank portion has a plurality of teeth formed exteriorly on the rear end thereof, said anvil member being rotatable with and relative to said hammer member, radially extending impact receiving means formed on said anvil member forward of said hammer member and adjacent the front surface thereof, a pair of diametrically oppositely disposed generally cylindrical jaw members mounted in the front end of said hammer member for rotation therewith around the central axis of said hammer member and for reciprocating axial movement parallel to said axis, means resiliently urging each of said jaw members into a rearward position wherein the front ends thereof are disposed rearwardly of said impact receiving means, a pair of diametrically oppositely disposed rotary gears mounted against the inside of said flat face for actuation, respectively, of said jaw members and thereby being supported to rotate with said hammer member around the central axis thereof in a plane perpendicular to said axis, each of said rotary gears also being mounted to rotate about its own central axis in said plane and having an annular cam surface concentrically disposed on the forward face thereof, each of said rotary gears having the central axis thereof laterally offset inwardly from the central axis of said respective jaw member for a distance equal to the radius of said annular cam surface, each of said annular cam surfaces being in a plane parallel to said plane and having a single cam lobe projecting forwardly for engagement with the rear end of the associated jaw member for carnming the latter forwardly, which lobe occupies less than a 90 degree sector of said annular cam surface, whereby forward sliding movement is imparted to said jaw members by said lobes once during a single revolution of said rotary gears about the respective central axes thereof, each of said rotary gears having teeth at the periphery thereof engageable with the teeth of said shank portion of said anvil for rotating each of said rotary gears one revolution relative to said hammer member during a predetermined number of revolutions of said hammer member relative to the :anvil, whereby when rotary movement of said anvil is restrained, said hammer member is rotated relative to said anvil member thereby projecting said jaw members forwardly into position for delivering impact blows to said impact receiving means once during said predetermined number of revolutions of said hammer member, each of said jaw members being fully cammed forwardly in advance of striking the impact receiving means so that each of said cam lobes is disengaged from the rear end of the associated jaw member at the time of impact thereby to permit said resilient means to return each jaw member to its rearward position.

References Cited by the Examiner UNITED STATES PATENTS 2,339,530 1/44 Van Sittert et a1 l9230.5 2,339,531 1/44 Van Sittert et a1. 192-30.5 2,784,818 3/57 Maurer 192-30.5 2,836,272 5/58 Kaman 192-305 DAVID J. WILLIAMOWSKY, Primary Examiner. 

1. IN A ROTARY IMPACT TOOL HAVING ROTARY MOTOR MEANS, A ROTARY IMPACT MECHANISM COMPRISING, A HAMMER MEMBER OPERABLY CONNECTED TO SAID ROTARY MOTOR MEANS FOR ROTATION THEREWITH, A GENERALLY CYLINDRICAL ANVIL MEMBER HAVING A SHANK PORTION EXTENDING CO-AXIALLY INTO SAID HAMMER MEMBER, SAID ANVIL MEMBER BEING ROTATABLE WITH AND RELATIVE TO SAID HAMMER MEMBER, RADIALLY EXTENDING IMPACT RECEIVING MEANS FORMED ON SAID ANVIL MEMBER FORWARD OF SAID HAMMER MEMBER AND ADJACENT THE FRONT SURFACE THEREOF, A PLURALITY OF EQUALLY SPACED JAW MEMBERS MOUNTED IN SAID HAMMER MEMBER FOR ROTATION THEREWITH AROUND THE CENTRAL AXIS OF SAID HAMMER MEMBER AND FOR RECIPROCATING MOVEMENT PARALLEL TO SAID AXIS, MEANS RESILIENTLY URGING EACH OF SAID JAW MEMBERS INTO A REARWARD POSITION WHEREIN THE FRONT ENDS THEREOF ARE DISPOSED REARWARDLY OF SAID IMPACT RECEIVING MEANS, A PLURALITY OF ROTARY CAM MEMBERS MOUNTED IN THE REAR END OF SAID HAMMER MEMBER FOR ACTUATION, RESPECTIVELY, OF SAID JAW MEMBERS, SAID ROTARY CAM MEMBERS BEING MOUNTED TO ROTATE WITH SAID HAMMER MEMBER AROUND THE CENTRAL AXIS THEREOF IN A PLANE PERPENDICULAR TO SAID AXIS, EACH OF SAID ROTARY CAM MEMBERS ALSO BEING MOUNTED TO ROTATE ABOUT ITS OWN CENTRAL AXIS AND HAVING A CAM SURFACE THEREON ADAPTED FOR ENGAGEMENT WITH THE REAR END OF THE ASSOCIATED JAW MEMBER FOR CAMMING THE LATTER FORWARDLY, WHEREBY FORWARD SLIDING MOVEMENT IS IMPARTED TO SAID JAW MEMBERS DURING ROTATION OF SAID ROTARY CAM MEMBERS ABOUT THE RESPECTIVE CENTRAL AXES THEREOF, MEANS FOR ROTATING SAID ROTARY CAM MEMBERS ONE REVOLUTION ABOUT THE RESPECTIVE CENTRAL AXES THEREOF DURING A PREDETERMINED NUMBER OF REVOLUTIONS OF SAID HAMMER MEMBER RELATIVE TO THE ANVIL, WHEREBY SAID JAW MEMBERS ARE PROJECTED FORWARD INTO POSITION FOR DELIVERING IMPACT BLOWS TO SAID IMPACT RECEIVING MEANS ONCE DURING SAID PREDETERMINED NUMBER OF REVOLUTIONS OF SAID HAMMER MEMBER, EACH OF SAID JAW MEMBERS BEING FULLY CAMMED FORWARDLY IN ADVANCE OF STRIKING THE IMPACT RECEIVING MEANS SO THAT EACH OF SAID CAM SURFACES IS DISENGAGED FROM THE REAR END OF THE ASSOCIATED JAW MEMBER AT THE TIME OF IMPACT THEREBY TO PERMIT SAID RESILIENT MEANS TO RETURN EACH JAW MEMBER TO ITS REARWARD POSITION. 